package com.atguigu.src7;///*
// * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
// * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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//
//package java.util;
//import java.io.*;
//
///**
// * <p>Hash table and linked list implementation of the <tt>Map</tt> interface,
// * with predictable iteration order.  This implementation differs from
// * <tt>HashMap</tt> in that it maintains a doubly-linked list running through
// * all of its entries.  This linked list defines the iteration ordering,
// * which is normally the order in which keys were inserted into the map
// * (<i>insertion-order</i>).  Note that insertion order is not affected
// * if a key is <i>re-inserted</i> into the map.  (A key <tt>k</tt> is
// * reinserted into a map <tt>m</tt> if <tt>m.put(k, v)</tt> is invoked when
// * <tt>m.containsKey(k)</tt> would return <tt>true</tt> immediately prior to
// * the invocation.)
// *
// * <p>This implementation spares its clients from the unspecified, generally
// * chaotic ordering provided by {@link HashMap} (and {@link Hashtable}),
// * without incurring the increased cost associated with {@link TreeMap}.  It
// * can be used to produce a copy of a map that has the same order as the
// * original, regardless of the original map's implementation:
// * <pre>
// *     void foo(Map m) {
// *         Map copy = new LinkedHashMap(m);
// *         ...
// *     }
// * </pre>
// * This technique is particularly useful if a module takes a map on input,
// * copies it, and later returns results whose order is determined by that of
// * the copy.  (Clients generally appreciate having things returned in the same
// * order they were presented.)
// *
// * <p>A special {@link #LinkedHashMap(int,float,boolean) constructor} is
// * provided to create a linked hash map whose order of iteration is the order
// * in which its entries were last accessed, from least-recently accessed to
// * most-recently (<i>access-order</i>).  This kind of map is well-suited to
// * building LRU caches.  Invoking the <tt>put</tt> or <tt>get</tt> method
// * results in an access to the corresponding entry (assuming it exists after
// * the invocation completes).  The <tt>putAll</tt> method generates one entry
// * access for each mapping in the specified map, in the order that key-value
// * mappings are provided by the specified map's entry set iterator.  <i>No
// * other methods generate entry accesses.</i> In particular, operations on
// * collection-views do <i>not</i> affect the order of iteration of the backing
// * map.
// *
// * <p>The {@link #removeEldestEntry(Map.Entry)} method may be overridden to
// * impose a policy for removing stale mappings automatically when new mappings
// * are added to the map.
// *
// * <p>This class provides all of the optional <tt>Map</tt> operations, and
// * permits null elements.  Like <tt>HashMap</tt>, it provides constant-time
// * performance for the basic operations (<tt>add</tt>, <tt>contains</tt> and
// * <tt>remove</tt>), assuming the hash function disperses elements
// * properly among the buckets.  Performance is likely to be just slightly
// * below that of <tt>HashMap</tt>, due to the added expense of maintaining the
// * linked list, with one exception: Iteration over the collection-views
// * of a <tt>LinkedHashMap</tt> requires time proportional to the <i>size</i>
// * of the map, regardless of its capacity.  Iteration over a <tt>HashMap</tt>
// * is likely to be more expensive, requiring time proportional to its
// * <i>capacity</i>.
// *
// * <p>A linked hash map has two parameters that affect its performance:
// * <i>initial capacity</i> and <i>load factor</i>.  They are defined precisely
// * as for <tt>HashMap</tt>.  Note, however, that the penalty for choosing an
// * excessively high value for initial capacity is less severe for this class
// * than for <tt>HashMap</tt>, as iteration times for this class are unaffected
// * by capacity.
// *
// * <p><strong>Note that this implementation is not synchronized.</strong>
// * If multiple threads access a linked hash map concurrently, and at least
// * one of the threads modifies the map structurally, it <em>must</em> be
// * synchronized externally.  This is typically accomplished by
// * synchronizing on some object that naturally encapsulates the map.
// *
// * If no such object exists, the map should be "wrapped" using the
// * {@link Collections#synchronizedMap Collections.synchronizedMap}
// * method.  This is best done at creation time, to prevent accidental
// * unsynchronized access to the map:<pre>
// *   Map m = Collections.synchronizedMap(new LinkedHashMap(...));</pre>
// *
// * A structural modification is any operation that adds or deletes one or more
// * mappings or, in the case of access-ordered linked hash maps, affects
// * iteration order.  In insertion-ordered linked hash maps, merely changing
// * the value associated with a key that is already contained in the map is not
// * a structural modification.  <strong>In access-ordered linked hash maps,
// * merely querying the map with <tt>get</tt> is a structural
// * modification.</strong>)
// *
// * <p>The iterators returned by the <tt>iterator</tt> method of the collections
// * returned by all of this class's collection view methods are
// * <em>fail-fast</em>: if the map is structurally modified at any time after
// * the iterator is created, in any way except through the iterator's own
// * <tt>remove</tt> method, the iterator will throw a {@link
// * ConcurrentModificationException}.  Thus, in the face of concurrent
// * modification, the iterator fails quickly and cleanly, rather than risking
// * arbitrary, non-deterministic behavior at an undetermined time in the future.
// *
// * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
// * as it is, generally speaking, impossible to make any hard guarantees in the
// * presence of unsynchronized concurrent modification.  Fail-fast iterators
// * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
// * Therefore, it would be wrong to write a program that depended on this
// * exception for its correctness:   <i>the fail-fast behavior of iterators
// * should be used only to detect bugs.</i>
// *
// * <p>This class is a member of the
// * <a href="{@docRoot}/../technotes/guides/collections/index.html">
// * Java Collections Framework</a>.
// *
// * @param <K> the type of keys maintained by this map
// * @param <V> the type of mapped values
// *
// * @author  Josh Bloch
// * @see     Object#hashCode()
// * @see     Collection
// * @see     Map
// * @see     HashMap
// * @see     TreeMap
// * @see     Hashtable
// * @since   1.4
// */
//
//public class LinkedHashMap<K,V>
//    extends HashMap<K,V>
//    implements Map<K,V>
//{
//
//    private static final long serialVersionUID = 3801124242820219131L;
//
//    /**
//     * The head of the doubly linked list.
//     */
//    private transient Entry<K,V> header;
//
//    /**
//     * The iteration ordering method for this linked hash map: <tt>true</tt>
//     * for access-order, <tt>false</tt> for insertion-order.
//     *
//     * @serial
//     */
//    private final boolean accessOrder;
//
//    /**
//     * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance
//     * with the specified initial capacity and load factor.
//     *
//     * @param  initialCapacity the initial capacity
//     * @param  loadFactor      the load factor
//     * @throws IllegalArgumentException if the initial capacity is negative
//     *         or the load factor is nonpositive
//     */
//    public LinkedHashMap(int initialCapacity, float loadFactor) {
//        super(initialCapacity, loadFactor);
//        accessOrder = false;
//    }
//
//    /**
//     * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance
//     * with the specified initial capacity and a default load factor (0.75).
//     *
//     * @param  initialCapacity the initial capacity
//     * @throws IllegalArgumentException if the initial capacity is negative
//     */
//    public LinkedHashMap(int initialCapacity) {
//        super(initialCapacity);
//        accessOrder = false;
//    }
//
//    /**
//     * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance
//     * with the default initial capacity (16) and load factor (0.75).
//     */
//    public LinkedHashMap() {
//        super();
//        accessOrder = false;
//    }
//
//    /**
//     * Constructs an insertion-ordered <tt>LinkedHashMap</tt> instance with
//     * the same mappings as the specified map.  The <tt>LinkedHashMap</tt>
//     * instance is created with a default load factor (0.75) and an initial
//     * capacity sufficient to hold the mappings in the specified map.
//     *
//     * @param  m the map whose mappings are to be placed in this map
//     * @throws NullPointerException if the specified map is null
//     */
//    public LinkedHashMap(Map<? extends K, ? extends V> m) {
//        super(m);
//        accessOrder = false;
//    }
//
//    /**
//     * Constructs an empty <tt>LinkedHashMap</tt> instance with the
//     * specified initial capacity, load factor and ordering mode.
//     *
//     * @param  initialCapacity the initial capacity
//     * @param  loadFactor      the load factor
//     * @param  accessOrder     the ordering mode - <tt>true</tt> for
//     *         access-order, <tt>false</tt> for insertion-order
//     * @throws IllegalArgumentException if the initial capacity is negative
//     *         or the load factor is nonpositive
//     */
//    public LinkedHashMap(int initialCapacity,
//                         float loadFactor,
//                         boolean accessOrder) {
//        super(initialCapacity, loadFactor);
//        this.accessOrder = accessOrder;
//    }
//
//    /**
//     * Called by superclass constructors and pseudoconstructors (clone,
//     * readObject) before any entries are inserted into the map.  Initializes
//     * the chain.
//     */
//    @Override
//    void init() {
//        header = new Entry<>(-1, null, null, null);
//        header.before = header.after = header;
//    }
//
//    /**
//     * Transfers all entries to new table array.  This method is called
//     * by superclass resize.  It is overridden for performance, as it is
//     * faster to iterate using our linked list.
//     */
//    @Override
//    void transfer(HashMap.Entry[] newTable, boolean rehash) {
//        int newCapacity = newTable.length;
//        for (Entry<K,V> e = header.after; e != header; e = e.after) {
//            if (rehash)
//                e.hash = (e.key == null) ? 0 : hash(e.key);
//            int index = indexFor(e.hash, newCapacity);
//            e.next = newTable[index];
//            newTable[index] = e;
//        }
//    }
//
//
//    /**
//     * Returns <tt>true</tt> if this map maps one or more keys to the
//     * specified value.
//     *
//     * @param value value whose presence in this map is to be tested
//     * @return <tt>true</tt> if this map maps one or more keys to the
//     *         specified value
//     */
//    public boolean containsValue(Object value) {
//        // Overridden to take advantage of faster iterator
//        if (value==null) {
//            for (Entry e = header.after; e != header; e = e.after)
//                if (e.value==null)
//                    return true;
//        } else {
//            for (Entry e = header.after; e != header; e = e.after)
//                if (value.equals(e.value))
//                    return true;
//        }
//        return false;
//    }
//
//    /**
//     * Returns the value to which the specified key is mapped,
//     * or {@code null} if this map contains no mapping for the key.
//     *
//     * <p>More formally, if this map contains a mapping from a key
//     * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
//     * key.equals(k))}, then this method returns {@code v}; otherwise
//     * it returns {@code null}.  (There can be at most one such mapping.)
//     *
//     * <p>A return value of {@code null} does not <i>necessarily</i>
//     * indicate that the map contains no mapping for the key; it's also
//     * possible that the map explicitly maps the key to {@code null}.
//     * The {@link #containsKey containsKey} operation may be used to
//     * distinguish these two cases.
//     */
//    public V get(Object key) {
//        Entry<K,V> e = (Entry<K,V>)getEntry(key);
//        if (e == null)
//            return null;
//        e.recordAccess(this);
//        return e.value;
//    }
//
//    /**
//     * Removes all of the mappings from this map.
//     * The map will be empty after this call returns.
//     */
//    public void clear() {
//        super.clear();
//        header.before = header.after = header;
//    }
//
//    /**
//     * LinkedHashMap entry.
//     */
//    private static class Entry<K,V> extends HashMap.Entry<K,V> {
//        // These fields comprise the doubly linked list used for iteration.
//        Entry<K,V> before, after;
//
//        Entry(int hash, K key, V value, HashMap.Entry<K,V> next) {
//            super(hash, key, value, next);
//        }
//
//        /**
//         * Removes this entry from the linked list.
//         */
//        private void remove() {
//            before.after = after;
//            after.before = before;
//        }
//
//        /**
//         * Inserts this entry before the specified existing entry in the list.
//         */
//        private void addBefore(Entry<K,V> existingEntry) {
//            after  = existingEntry;
//            before = existingEntry.before;
//            before.after = this;
//            after.before = this;
//        }
//
//        /**
//         * This method is invoked by the superclass whenever the value
//         * of a pre-existing entry is read by Map.get or modified by Map.set.
//         * If the enclosing Map is access-ordered, it moves the entry
//         * to the end of the list; otherwise, it does nothing.
//         */
//        void recordAccess(HashMap<K,V> m) {
//            LinkedHashMap<K,V> lm = (LinkedHashMap<K,V>)m;
//            if (lm.accessOrder) {
//                lm.modCount++;
//                remove();
//                addBefore(lm.header);
//            }
//        }
//
//        void recordRemoval(HashMap<K,V> m) {
//            remove();
//        }
//    }
//
//    private abstract class LinkedHashIterator<T> implements Iterator<T> {
//        Entry<K,V> nextEntry    = header.after;
//        Entry<K,V> lastReturned = null;
//
//        /**
//         * The modCount value that the iterator believes that the backing
//         * List should have.  If this expectation is violated, the iterator
//         * has detected concurrent modification.
//         */
//        int expectedModCount = modCount;
//
//        public boolean hasNext() {
//            return nextEntry != header;
//        }
//
//        public void remove() {
//            if (lastReturned == null)
//                throw new IllegalStateException();
//            if (modCount != expectedModCount)
//                throw new ConcurrentModificationException();
//
//            LinkedHashMap.this.remove(lastReturned.key);
//            lastReturned = null;
//            expectedModCount = modCount;
//        }
//
//        Entry<K,V> nextEntry() {
//            if (modCount != expectedModCount)
//                throw new ConcurrentModificationException();
//            if (nextEntry == header)
//                throw new NoSuchElementException();
//
//            Entry<K,V> e = lastReturned = nextEntry;
//            nextEntry = e.after;
//            return e;
//        }
//    }
//
//    private class KeyIterator extends LinkedHashIterator<K> {
//        public K next() { return nextEntry().getKey(); }
//    }
//
//    private class ValueIterator extends LinkedHashIterator<V> {
//        public V next() { return nextEntry().value; }
//    }
//
//    private class EntryIterator extends LinkedHashIterator<Map.Entry<K,V>> {
//        public Map.Entry<K,V> next() { return nextEntry(); }
//    }
//
//    // These Overrides alter the behavior of superclass view iterator() methods
//    Iterator<K> newKeyIterator()   { return new KeyIterator();   }
//    Iterator<V> newValueIterator() { return new ValueIterator(); }
//    Iterator<Map.Entry<K,V>> newEntryIterator() { return new EntryIterator(); }
//
//    /**
//     * This override alters behavior of superclass put method. It causes newly
//     * allocated entry to get inserted at the end of the linked list and
//     * removes the eldest entry if appropriate.
//     */
//    void addEntry(int hash, K key, V value, int bucketIndex) {
//        super.addEntry(hash, key, value, bucketIndex);
//
//        // Remove eldest entry if instructed
//        Entry<K,V> eldest = header.after;
//        if (removeEldestEntry(eldest)) {
//            removeEntryForKey(eldest.key);
//        }
//    }
//
//    /**
//     * This override differs from addEntry in that it doesn't resize the
//     * table or remove the eldest entry.
//     */
//    void createEntry(int hash, K key, V value, int bucketIndex) {
//        HashMap.Entry<K,V> old = table[bucketIndex];
//        Entry<K,V> e = new Entry<>(hash, key, value, old);
//        table[bucketIndex] = e;
//        e.addBefore(header);
//        size++;
//    }
//
//    /**
//     * Returns <tt>true</tt> if this map should remove its eldest entry.
//     * This method is invoked by <tt>put</tt> and <tt>putAll</tt> after
//     * inserting a new entry into the map.  It provides the implementor
//     * with the opportunity to remove the eldest entry each time a new one
//     * is added.  This is useful if the map represents a cache: it allows
//     * the map to reduce memory consumption by deleting stale entries.
//     *
//     * <p>Sample use: this override will allow the map to grow up to 100
//     * entries and then delete the eldest entry each time a new entry is
//     * added, maintaining a steady state of 100 entries.
//     * <pre>
//     *     private static final int MAX_ENTRIES = 100;
//     *
//     *     protected boolean removeEldestEntry(Map.Entry eldest) {
//     *        return size() > MAX_ENTRIES;
//     *     }
//     * </pre>
//     *
//     * <p>This method typically does not modify the map in any way,
//     * instead allowing the map to modify itself as directed by its
//     * return value.  It <i>is</i> permitted for this method to modify
//     * the map directly, but if it does so, it <i>must</i> return
//     * <tt>false</tt> (indicating that the map should not attempt any
//     * further modification).  The effects of returning <tt>true</tt>
//     * after modifying the map from within this method are unspecified.
//     *
//     * <p>This implementation merely returns <tt>false</tt> (so that this
//     * map acts like a normal map - the eldest element is never removed).
//     *
//     * @param    eldest The least recently inserted entry in the map, or if
//     *           this is an access-ordered map, the least recently accessed
//     *           entry.  This is the entry that will be removed it this
//     *           method returns <tt>true</tt>.  If the map was empty prior
//     *           to the <tt>put</tt> or <tt>putAll</tt> invocation resulting
//     *           in this invocation, this will be the entry that was just
//     *           inserted; in other words, if the map contains a single
//     *           entry, the eldest entry is also the newest.
//     * @return   <tt>true</tt> if the eldest entry should be removed
//     *           from the map; <tt>false</tt> if it should be retained.
//     */
//    protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {
//        return false;
//    }
//}
